Crack Paths 2009

Mixed-mode fracture mechanics concepts were required as the discontinuity was

intrinsic to the welded joint.

Cylinder

End cap

Figure 2 - Detail of the welded joint

Two cases were assumed: the first (Type H) that the discontinuity has the d and c

dimensions given in the part drawing, the second that weld deposition reduced d=0

(Type V). The two types of crack of Fig. 3 were investigated by F E Musing the

discontinuity dimensions and the corresponding stress intensity factors computed. A

a)

b)

Figure 3 – Local deformation, elastic stress distribution and crack path

a)

for a) V crack; b) Hcrack. Scale x100.

(Note that models are rotated 90- deg clockwise respect to Fig. 2)

The Mises stress distribution for the two crack configurations shown in Fig. 3 reveals a

local singularity and a tilt of the iso-stress lines with respect to the discontinuity plane.

Fracture mechanics identifies a mixed-mode loading condition, which affects crack

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